Distinguishing neuromuscular disorders based on the passive electrical material properties of muscle

The passive electrical properties of muscle, including conductivity and permittivity and their directional dependence, may be altered in neuromuscular disease; however, the character of these alterations is unknown.

Fifteen wild-type mice, 13 amyotrophic lateral sclerosis mice, 9 muscular dystrophy (mdx) mice, and 15 mice with induced disuse atrophy were euthanized, and the gastrocnemius was excised. A 50-kHz current was applied immediately to the ex vivo muscle, and its material properties were calculated.

The disease groups showed distinct material property values [F(12, 119) = 14.6, P < 0.001] according to MANOVA. Post-hoc tests confirmed that differences existed between all 4 groups. They were most pronounced in the mdx mice, which had markedly increased conductivity. Direction-dependent properties of current flow also were significantly different among the groups (P < 0.001).

These data confirm that the inherent passive electrical properties of muscle differ by disease type. We anticipate that similar data could eventually be obtained via surface measurements, providing an innovative approach to muscle disease diagnosis.